This invention relates to robotic devices and more particularly to a robotic gripper for use in picking up, transporting and dropping selected objects, particularly where the gripper must pass through tight areas to reach the object.
There are many applications in industry, government, (for example the post office), and other businesses or institutions where robotic mechanisms are used to lift and carry selected objects, for example containers for various items, from one place to another. Frequently, the areas of operation for such robotic mechanisms are very tight and require a mechanism having a thin profile, free of protrusions, in order for the robotic gripper mechanism to be maneuvered into a suitable position to perform the gripping and lifting operation. A simple, inexpensive mechanism capable of performing the gripper function, while still having a thin, protrusion-free profile for maneuvering through tight areas, does not currently exist.
Another problem for robotic gripper mechanisms when operating in tight areas is that, even with a thin profile, the mechanism may still strike an object when being lowered into a pickup position. Since the gripper mechanisms are frequently being moved at relatively high speed to achieve good throughput rate, such inadvertent striking of an obstruction in a mechanism path may cause significant damage to the gripper mechanism, resulting in a costly shutdown of the entire system in which it is being utilized, and may also damage the object providing the obstruction. It is therefore desirable that a simple and inexpensive mechanism be provided to protect the gripper mechanism and prevent damage thereto in the event an obstruction is inadvertently encountered when the gripper mechanism is being lowered into an operative position. Again, a such simple and inexpensive protection mechanism does not currently exist.
In accordance with the above, this invention provides a robotic gripper mechanism which includes a housing, a gripper arm extending from said housing, a finger assembly mounted at a distal end of the arm, the finger assembly being normally biased to a retracted position, a slide moveable in the arm between a first inoperative position relative to the finger assembly and a second operative position, a drive member having at least a first and second state, and components operated by the drive member and operating on the slide in response to the state of the drive member such that the slide is in its first operative position when the drive member is in its first state and the slide is in its second operative position when the drive member is in its second state, the slide not influencing the position of the finger assembly when in its first position and acting on the finger assembly to move it to an extended operative position when the slide is in its second position.
The finger assembly may include at least one finger sized and shaped to, when the assembly is in its extended position, either fit under an object to be lifted, to fit in a corresponding receptacle in a side of the object, and/or to fit into a receptacle extending from the top of the object. The finger assembly may also be sized and shaped to fit through an opening form in the top of the object to be lifted when the assembly is in the retracted position and to grip the top of the object for lifting of the object when the assembly is moved to its operative position after passing through the opening. The finger assembly may also be movable, against its normal bias, when the slide moves from its second to its first position and there is weight on the finger assembly from an object being lifted, to a position where the object is released. Once the object is released, removing weight from the finger, the finger assembly operates under its bias to return to its retracted position.
The components between the drive member and the slide may be a mechanical linkage which mechanically attaches the drive member to the slide, the drive member preferably being a pneumatic cylinder. The finger assembly is preferably rotated about a pivot between its retracted and extended position, the mechanism preferably including a bias spring acting on the finger assembly to normally maintain it in its retracted position. At least one component may be provided which facilitates tension adjustment on the spring, and thus the bias force applied to the finger assembly.
The components between the drive member and slide may alternatively include a pivot arm and a mechanical linkage between the drive member and the pivot arm, the linkage pivoting the pivot arm out of contact with the slide when the drive member is in its first state and pivoting the pivot arm to bear against the slide in a manner to move and hold the slide in its second position when the drive member is in the second state. A biasing mechanism may be provided which moves the slide to its first inoperative position when the pivot arm is out of contact therewith.
The housing, including the gripper arm, may be positionable, at least vertically, to bring the gripper arm into position to perform a gripping operation and a mechanism may be provided which permits retraction of the gripper arm to protect the gripper arm when, during a downward vertical positioning of the housing, an obstacle is encountered by the gripper arm. The mechanism which permits retraction may include a mechanism for frictionally maintaining a vertical position for the gripper arm, friction applied to the gripper arm by such mechanism being sufficiently low that the gripper arm may overcome the friction and move up relative to the housing when an obstacle is encountered. The mechanism may also include an element for selectively removing the friction from the gripper arm when the arm is in a raised position, permitting the gripper arm to return to its normal position relative to the housing, and for then restoring frictional engagement with the arm. Alternatively, gravity alone may maintain the vertical position of the gripper arm, facilitating easy movement of the arm when an obstacle is encountered. A detector may be provided which indicates the position of the gripper arm relative to the housing. While the mechanism which permits retraction is preferably used in conjunction with the alternative component embodiment, it may also be utilized with other embodiments of the invention.
In accordance with another aspect of the invention, a robotic gripper mechanism is provided which includes the housing, the gripper arm extending from the housing and the finger assembly mounted at the distal end of the arm. The housing, including the gripper arm and finger assembly, are positionable, at least vertically, to bring the gripper arm into position to perform a gripper operation, and a mechanism is provided which permits retraction of the gripper arm to protect the arm and the finger assembly when, during a downward vertical positioning of the housing, an obstacle is encountered by the gripper arm. The mechanism which permits retraction may include a mechanism for frictionally maintaining a vertical position of the gripper arm with a friction sufficiently low that the gripper arm may overcome the friction and move up relative to the housing when an obstacle is encountered and an element may be provided for selectively removing the friction from the gripper arm when the arm is in a raised position, permitting the gripper arm to return to its normal position relative to the housing, and for then restoring frictional engagement of the arm. A detector may also be provided which indicates the position of the gripper arm relative to the housing. The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings, the same or related reference numerals being utilized for common elements in the various figures.